RESTORING THE BRAKE SYSTEM OF A 1972 V12 FERRARI 365 GTC 4
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The braking system is a twin circuit hydraulic which operates on four x four piston callipers. The dual pipe system is fed from a tandem master cylinder mounted on the inner wing on the drivers side close to the fluid reservoir.There are ventilated discs on all four wheels with a cable operated handbrake on a set of handbrake shoes inside a drum disc arrangement at the rear wheels. Assistance to stop this heavy car is provided by a Bonaldi servo on the firewall close to the master cylinder & fluid reservoir.  |
The braking system on this GTC4 was shot. The ATE callipers were in a bad state & the whole system required a total rebuild.Fortunately overhaul kits & new calliper pistons were readily available from ATE brake equipment specialists in the UK. The callipers were completely dismantled & the external & non-functional internal surfaces bead blasted to remove years of debris.All fluid passages & piston bores were occluded prior to electroless nickel plating the units.These are the four completely overhauled callipers prior to refitting. A total overhaul of the whole system was needed & I was taking no chances with a near two ton 150mph motor car. Any car that stands around for a significant period of time should have the brake fluid changed regularly as the hygroscopic fluid absorbs much water over time. The brake master cylinder was removed, stripped down & all seals were replaced Fortunately the bore & piston were in excellent condition with no score marks visible. |
The braking system was functional but after examining the brake pipes & other components I am not at all sure sure how. The callipers were not attached to the hubs with the correct bolts & three of them were bolted in place with a threaded bolt & a string of 7 or 8 washers. The fluid that I drained from the system & clearly would not have been functioning properly.The pads were worn almost down to the metal backing & I am glad I took it really easy on my 180 mile drive home. The state of the brake system components & the very old brake fluid was a real let down & I do not believe the system was working anywhere near properly.A so called expert garage maintaining this car had left the braking system mostly untouched over many years.It appeared that the service was limited to oil changes,taking for MOT at a not too observant MOT station & not much else. |
 The brake servo vacuum is created by a vacuum pump driven directly by a key off the front of the inlet valve camshaft oft the left cylinder bank. The vacuum to the servo unit is conveyed by a reinforced tube between the pump & the unit itself |
 The servo unit itself was definitely in need of repair & there was fluid slopping around within the outer casing I do not know how but despite it working reasonably all was not as it should be.I had the unit overhauled by a local brake equipment specialist who had also redone the callipers & master cylinder |
 The brake pipes were so badly corroded they required replacement and an off the shelf set was not available.I made a new set of pipes of copper nickel alloy using a specialist pipe flaring tool & a pipe bender.Tighter curves aroundsuitably sized round tool.Each pipe was removed & clearly marked & a new replacement was made. Replacing the pipes in the engine bay without the engine in place was relatively simple. |
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Replacing the two long brake pipes from the master cylinder to the rear which travelled the length of the car in the driver side sill was a difficult task. I removed the original pipes after attaching lengths of flexible wire to the ends so it would be possible to pull the new pipes through.The narrow channel also contained the fuel return breather hose so threading the brake pipes front to back was tight squeeze.I filled the internal sill with Waxoyl after all the work was done prior to sealing both ends. |
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The rear brake pressure limiters had clearly seen better days although the brakes still worked somewhat poorly. These units are positioned well out harms way in the chassis close to the differential & are not easy to access. The outer casing of one unit was broken & was held in place by the brake pipes alone.There are serviceable parts in the ATE limiters and I was pleasantly surprised to find two new units in stock at Ferrari UK. |
This is the top section of the handbrake lever assembly which connects to the handbrake lever.A single wire cable runs through the small pulley & connects both pairs of handbrake shoes on a special disc/drum assembly. The existing system was completely seized so how does a car with a totally defective handbrake achieve MOT standard. After reassembly the handbrake,not the most efficient arrangement, was easily able to reach the requires standard to pass the MOT inspection |
The complete brake system comprising master cylinder,brake servo, callipers were overhauled & both rear wheel pressure limiting devices replaced A new set of brake pipes, disc pads, brake shoes were fitted plus new brake fluid after draining what had become almost dirty water.The brakes now work extremely well & are capable of stopping an almost 2 ton car with ease.I have not tested them fully but an emergency stop pulls my GTC4 up smoothly & in a straight line. |